Electrochemical device, in particular electrolysis device

Abstract

An electrochemical device (10'), with a cell stack consisting of a plurality of cell stack elements, with a force application unit (13) which exerts a force on the cell stack in order to press the cell stack elements of the cell stack fluid-tightly in sealing regions (17) of the cell stack, wherein the force application unit (13) is designed in such a manner that the force for pressing the cell stack acts on the cell stack and therefore on the sealing regions (17) of the cell stack depending on the operating state of the electrochemical device (10').

Description

[0001] Electrochemical device, in particular electrolysis device

[0002] The invention relates to an electrochemical device designed in particular as an electrolysis device.

[0003] DE 10 2017 108 413 A1 discloses an electrochemical device designed as an electrolysis device with a cell stack composed of a plurality of cell stack elements. Furthermore, the electrolysis device known from this prior art comprises a force application unit, via which a force can be exerted on the cell stack in order to press the cell stack elements of the cell stack together in a fluid-tight manner. The cell stack elements comprise sealing elements or provide sealing elements that are pressed against one another or onto one another in a fluid-tight manner by the force provided by the force application unit, forming sealing regions of the cell stack. In the electrolysis device known from DE 10 2017 108 413 A1, the force application unit comprises end plates between which the cell stack is arranged. Furthermore, the force application unit comprises spring elements, the spring force of which presses the end plates against one another, pressing the cell stack together.Struts extend between the end plates, with the spring elements interacting with the struts to press the end plates against each other.

[0004] As a result of the compression of the cell stack elements, forces act on the cell stack elements and thus on the sealing elements and thus on the sealing areas of the cell stack. In electrochemical devices known from practice, the cell stack elements are pressed together in every operating state of the electrochemical device, so that in all operating states the force for compressing the cell stack acts on the cell stack elements and thus the sealing areas. As a result of such permanent compressive stress, particularly in combination with high temperatures and voltage fluctuations, the sealing elements and thus the sealing areas can tend to relax. As a result, the sealing areas then lose their sealing effect. This limits the service life of the electrochemical device, since leaky sealing areas can lead to total failure of the electrochemical device.

[0005] There is a need for an electrochemical device, particularly designed as an electrolysis device, that has a longer service life. Based on this, the present invention is based on the object of creating a novel electrochemical device, particularly designed as an electrolysis device. This object is achieved by an electrochemical device according to claim 1. The force application unit is designed such that the force for pressing the cell stack acts on the cell stack and thus on the sealing areas depending on the operating state of the electrochemical device.

[0006] The invention proposes that the force application unit is designed such that the force provided by it for pressing the cell stack acts on the cell stack and thus the sealing areas thereof depending on the operating state of the electrochemical device. The pressing of the cell stack therefore only takes place in those operating states of the electrolysis device in which this is necessary for the operation of the electrochemical device, i.e. when hydrogen H2 is to be produced in an electrolysis device. Outside of such production operation of the electrochemical device, i.e. during transport or maintenance work or in standby mode, i.e. when an electrochemical device designed as an electrolysis device is not producing hydrogen H2, the force for pressing the cell stack does not act on the cell stack and thus the sealing areas thereof, or only acts to a reduced extent.This can counteract relaxation of the sealing elements and thus of the sealing regions. The electrochemical device then has an increased service life. The force application unit is preferably designed such that, in an active operating state of the electrochemical device, the force for compressing the cell stack acts to a first extent on the cell stack and thus on the sealing regions thereof, and that, in an inactive operating state of the electrochemical device, the force for compressing the cell stack does not act on the cell stack or acts to a second extent, which is smaller than the first extent, and thus on the sealing regions thereof. This is particularly preferred in order to increase the service life of the electrochemical device.

[0007] The force application unit preferably has end plates between which the cell stack is arranged. The force application unit has at least one spring element whose spring force is designed to compress the end plates while pressing the cell stack together. The force application unit has at least one force-absorbing element which is designed to at least partially absorb the spring force provided by the at least one spring element depending on the operating state of the electrochemical device and thus to at least reduce the force acting on the cell stack and thus on the sealing regions. When no sealing effect is required, the force for pressing the cell stack can be at least partially absorbed via the at least one force-absorbing element. This allows a reduction in the relaxation tendency of the sealing regions and thus an increase in the service life of the electrochemical device.

[0008] Preferably, the at least one force-absorbing element is arranged between the end plates, wherein the respective force-absorbing element comprises a cylinder unit with a cylinder, with a piston guided in the cylinder, and with at least one line that can be opened and closed by a valve for supplying and / or discharging an incompressible medium into the cylinder, wherein the valve is open or closed depending on the operating state of the electrochemical device. This design is structurally simple and therefore preferred in order to counteract the tendency towards relaxation and to increase the service life of the electrochemical device. Preferably, the valve is open in an active operating state of the electrochemical device, and closed in an inactive operating state of the electrochemical device. This allows a reduction in the tendency towards relaxation of the sealing regions and thus an increase in the service life of the electrochemical device.

[0009] Preferably, the cylinder of the respective force-absorbing element is supported on a first end plate, and the piston of the respective force-absorbing element is supported on a second end plate, wherein the cylinder and / or the piston of the respective force-absorbing element carries insulation that rests against the respective end plate. This can prevent an electrical short circuit between the end plates.

[0010] Preferably, a control unit automatically detects the operating state of the electrochemical device based on a measurement signal from at least one pressure sensor and automatically controls the force application unit based thereon. This is particularly preferred for automated operation of the force application unit to reduce the tendency to relaxation and increase the service life of the electrochemical device.

[0011] The electrochemical device is preferably designed as an electrolysis device that, in an active operating state, generates hydrogen H2 and oxygen O2 from water H2O. The electrochemical device is preferably an electrolysis device.

[0012] Preferred developments of the invention emerge from the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail with reference to the drawing, without being limited thereto. In the drawing: Fig. 1: a cross section through an electrolysis device

[0013] Electrochemical device together with detail I,

[0014] Fig. 2 is a schematic diagram of the electrochemical device of Fig. 1;

[0015] Fig. 3 is a diagram of an electrochemical device according to the invention;

[0016] Fig. 4 shows the diagram of Fig. 3 with a power flow in an active operating state of the electrochemical device;

[0017] Fig. 5 shows the scheme of Fig. 3 with a power flow in an active operating state of the electrochemical device;

[0018] Fig. 6 shows detail VI of the electrochemical device according to the invention;

[0019] Fig. 7 is a plan view of an electrochemical device according to the invention.

[0020] Fig. 1 shows a schematic of the structure of an electrochemical device 10 designed as an electrolysis device. The electrochemical device 10 has a cell stack 11 consisting of several cell stack elements 12, with detail I of Fig. 1 showing a section of the cell stack 11 with several cell stack elements 12. Detail I of Fig. 1 shows a membrane 12a as cell stack elements 12, which separates an anode 12b from a cathode 12c. Bipolar plates 12d, 12e are also shown. A transport layer 12f, 12g can be present on the anode side and on the cathode side, respectively. The region of the cell stack 11 in which the actual electrolysis takes place is referred to as the active area or active region 16.

[0021] The electrochemical device further comprises a force application unit 13. The force application unit 13 comprises end plates 14, 15, between which the cell stack 11 is arranged. The force application unit 13 can be used to compress the cell stack 11 in a fluid-tight manner by pressing the cell stack elements 12 arranged one above the other together in a fluid-tight manner. During operation, a pressure difference exists between the anode 12b and the cathode 12c. In order to seal the anode 12b from the cathode 12c and the anode 12b and cathode 12c from an environment 18, the cell stack elements 12—namely, in Fig. 1, the cell stack elements 12a, 12d, and 12e—are pressed together to form sealing regions 17. The cell stack elements 12d and 12e can carry or provide sealing elements 12h and 12i, respectively. A section of the membrane 12a also provides a sealing element for the respective sealing area 17.

[0022] As already explained, the cell stack elements 12 of the cell stack 11 to be pressed together are pressed together via the force application unit 13, which has the end plates 14, 15, namely via spring elements 19, which are shown in Fig.

[0023] 1 on the end plate 14. Fig. 1 also shows schematically struts 20 which extend between the end plates 14, 15, wherein the spring elements 19 are preferably assigned to the struts 20 such that in the region of each strut 20 a spring element 19 is present in order to press the two end plates 14, 15 via the spring elements 19 and struts 20.

[0024] Fig. 2 shows a schematic diagram of the electrochemical device 10 of Fig. 1, wherein Fig. 2 schematically shows the end plates 14, 15 of the force application unit 13 and sealing regions 17 formed by the pressed cell stack elements 12. Furthermore, Fig. 2 schematically shows a spring force F applied via the spring elements 19, which serves to press the cell stack elements 12 of the cell stack 11.

[0025] The structure of an electrochemical device 10 described with reference to Figs. 1 and 2 is known, for example, from DE 10 2017 108 413 A1. Fig. 3 shows a further development according to the invention of the electrochemical device 10 of Figs. 1 and 2, providing an electrochemical device 10' according to the invention, wherein in the electrochemical device 10' according to the invention, the force application unit 13 is designed such that the force F, which serves to press the cell stack 11 and thus the sealing regions 17, acts on the cell stack 11 and thus on the sealing regions 17 depending on the operating state of the electrochemical device 10.

[0026] The force application unit 13 is designed such that in an active operating state of the electrochemical device 10' the force for pressing the cell stack 11 acts to a first extent on the cell stack 11 and thus on the sealing regions 17 of the cell stack 11, and that in an inactive operating state of the electrochemical device 10' the force F for pressing the cell stack 11 does not act or acts to a second extent, which is smaller than the first extent, on the cell stack and thus on the sealing regions 17 of the cell stack 11.

[0027] Thus, Fig. 4 shows a force flow of the force F serving to press the cell stack 11 in the electrochemical device 10' according to the invention in an active operating state thereof, wherein according to Fig. 4 the spring force F acts in the direction of the force arrows 21 on the cell stack 11, namely on the sealing areas 17 thereof.

[0028] In Fig. 5, the force arrows 22 visualize that in an inactive operating state of the electrochemical device 10', the force flow of the spring force F of the at least one spring element 19 serving to compress the cell stack 11 does not act from the cell stack 11 and therefore does not act on the sealing regions 17 thereof, but rather, in the preferred exemplary embodiment shown, is absorbed by force absorbing elements 23 of the force application unit 13 of the electrochemical device 10' according to the invention. In an electrochemical device 10' designed as an electrolysis device, the active operating state of the electrochemical device 10' is the operating state in which hydrogen H2 and oxygen O2 are produced from water H2O. In an inactive operating state of an electrolysis device 10', no hydrogen H2 and oxygen O2 are produced from water H2O.The electrolysis device 10' can assume the inactive operating state either in standby mode or in switched-off mode, which it assumes for transport and maintenance purposes.

[0029] Fig. 6 shows detail VI of Fig. 3, wherein in Fig. 6 a respective force-absorbing element 23 of the force-applying unit 13 of the electrochemical device 10' is shown in greater detail. The force-absorbing element 23 is configured to at least partially absorb the spring force F provided by the at least one spring element 19 depending on the operating state of the electrochemical device 10' and thus to at least reduce the force acting on the cell stack 11 and thus on the sealing regions 17 thereof. In the inactive operating state of the electrochemical device 10', the at least one force-absorbing element 23 can completely absorb the spring force F provided by the spring elements 19, so that then, as shown in Fig. 5, no further force is introduced into the respective sealing region 17.

[0030] The respective force-absorbing element 23 is arranged at least partially between the end plates 14, 15. The respective force-absorbing element 23 thus has a cylinder unit 24 arranged between the end plates 14, 15, comprising a cylinder 25 and a piston 26 guided in the cylinder 25. A line 27 interacts with the cylinder 25 and is coupled to an expansion tank 28, into which a valve 29 is integrated. The line 27 can be opened and closed via the valve 29 in order to supply an incompressible medium, when the line 27 is opened, either from the expansion tank 28 to the cylinder 25 or in the opposite direction from the cylinder 25 into the expansion tank 28. The piston 26 is supported on the end plate 14, and the cylinder 25 is supported on the opposite end plate 15. Then, when the valve 29 is closed, the line 27 is blocked and does not allow the incompressible medium to flow out of the cylinder 25.

[0031] In Fig. 6, a spring 30 is also accommodated in the cylinder 24. The spring 30 ensures a defined preload of the piston 26 in order to press the piston 26 with a defined preload against the inside of the end plate 14. The contact force of the piston 26 against the end plate 14 is also dependent on the incompressible medium, which can flow between the expansion tank 28 and the cylinder 25 when the valve 29 is open, but which cannot flow between the expansion tank 28 and the cylinder 25 when the valve 29 is closed. When the electrochemical device 10' is active, i.e., when it is used to generate hydrogen H2 and oxygen O2 from water H2O, the valve 29 is open and the piston 26 is movable, so that the incompressible medium can flow from the cylinder 25 into the expansion tank 28 as a result of the action of the spring force F.A force flow derived from the spring force F is then directed into the cell stack 11, namely into the sealing regions 17 thereof, as shown in Fig. 4. If, however, the electrochemical device 10' is inactive, the valve 29 is closed and the piston 26 sits firmly in the cylinder 25. In this state, the spring force F in the sense of the force flow 22 in Fig. 5 is absorbed at least partially, preferably completely, by the force-absorbing element 23 depending on the position of the piston 26 in order to introduce less or no force into the sealing regions 17. The position of the piston 26 when the valve is closed depends on how much incompressible medium is located in the cylinder 25.

[0032] Fig. 7 shows a schematic plan view of the electrolysis device 10', namely of the end plate 14 of the force application unit 13. In Fig. 7, a cylinder unit 24 is arranged at each of four corner positions between the end plates 14, 15, which are coupled to a common compensation tank 28 via lines 27. When the electrochemical device 10' is active, the valve 29 is open; when the electrochemical device 10' is inactive, the valve 29 is closed. The invention can ensure that forces act on the cell stack 11, namely the sealing regions 17 thereof, only when this is necessary due to the operating mode or operating state of the electrochemical device 10'. Otherwise, the force of the spring elements 19 is absorbed by the cylinder units 24, so that no force or only a very low force is introduced into the sealing regions 17.This protects the sealing materials from relaxation, increasing the overall service life of the electrochemical device 10'.

[0033] In Fig. 6, the piston 26 carries insulation 31. The cylinder 25 can also carry insulation. With the respective insulation, the piston 26 rests on the end plate 14 in Fig. 1, and the cylinder 25 rests on the end plate 15. This prevents an electrical short circuit between the two end plates 14, 15.

[0034] The force application unit 13 is designed such that the force for pressing the cell stack 11 acts automatically on the cell stack 11 and thus on the sealing areas 17 of the cell stack 11 depending on the operating state of the electrochemical device 10'. For this purpose, the electrochemical device 10' has a control unit 33 which, depending on a measurement signal from at least one pressure sensor 32, automatically detects the operating state of the electrochemical device 10' and, depending thereon, automatically controls the force application unit 13, namely the or each valve 29.

[0035] The electrochemical device 10' is preferably an electrolysis device. However, it can also be a fuel cell. List of reference symbols

[0036] 10, 10' Electrochemistry device

[0037] 11 cell stacks

[0038] 12 cell stack element

[0039] 13 Force application unit

[0040] 14 End plate

[0041] 15 End plate

[0042] 16 active area

[0043] 17 Sealing area

[0044] 18 Surroundings

[0045] 19 Spring element

[0046] 20 struts

[0047] 21 Power Arrow

[0048] 22 Power Arrow

[0049] 23 Force absorption element

[0050] 24 cylinder unit

[0051] 25 cylinders

[0052] 26 pistons

[0053] 27 Line

[0054] 28 expansion tank

[0055] 29 Valve

[0056] 30 spring

[0057] 31 Isolation

[0058] 32 pressure sensor

[0059] 33 Control unit

Claims

Claims 1. Electrochemical device (10'), with a cell stack (11) made up of a plurality of cell stack elements (12), with a force application unit (13) which exerts a force on the cell stack (11) in order to press the cell stack elements (12) of the cell stack (11) in a fluid-tight manner in sealing regions (17) of the cell stack (11), characterized in that the force application unit (13) is designed such that the force for pressing the cell stack (11) acts on the cell stack (11) and thus on the sealing regions (17) of the cell stack (11) depending on the operating state of the electrochemical device (10').

2. Electrochemical device (10') according to claim 1, wherein the force application unit (13) is designed such that in an active operating state of the electrochemical device (10') the force for pressing the cell stack (11) acts to a first extent on the cell stack (11) and thus on the sealing regions (17) thereof, and in an inactive operating state of the electrochemical device (10') the force for pressing the cell stack (11) does not act or acts to a second extent, which is smaller than the first extent, on the cell stack (11) and thus on the sealing regions (17) thereof.

3. Electrochemical device (10') according to claim 1 or 2, wherein the force application unit (13) is designed such that the force for pressing the cell stack (11) acts automatically on the cell stack (11) and thus on the sealing regions (17) of the cell stack (11) depending on the operating state of the electrochemical device (10').

4. Electrochemical device (10') according to claim 1, 2 or 3, wherein the force application unit (13) has end plates (14, 15) between which the cell stack (11) is arranged, the force application unit (13) has at least one spring element (19) whose spring force is designed to compress the end plates (14, 15) while pressing the cell stack (11), the force application unit (13) has at least one force absorption element (23) which is designed to at least partially absorb the spring force provided by the at least one spring element (19) depending on the operating state of the electrochemical device (10') and thus at least reduce the force acting on the cell stack (11) and thus on the sealing regions (17) of the cell stack (11).

5. Electrochemical device (10') according to claim 4, wherein at least one force-absorbing element (23) is arranged between the end plates (14, 15), which has a cylinder unit (24) with a cylinder (25), with a piston (26) guided in the cylinder (25) and with at least one line (27) which can be opened and closed by a valve (29) for supplying and / or discharging an incompressible medium into and / or out of the cylinder (25) thereof, wherein the valve (29) is open or closed depending on the operating state of the electrochemical device (10').

6. Electrochemical device (10') according to claim 5, wherein in an active operating state of the electrochemical device (10') the valve (29) is open and in an inactive operating state of the electrochemical device the valve (29) is closed.

7. Electrochemical device (10') according to claim 5 or 6, wherein the cylinder (25) of the respective force-absorbing element (23) is supported on a first end plate (15) and the piston (26) of the respective force-absorbing element (23) is supported on a second end plate (14), the cylinder (25) and / or the piston (26) of the respective force-absorbing element (23) carries an insulation (31) which bears against the respective end plate (14, 15).

8. Electrochemical device (10') according to claim 6 or 7, wherein the cylinder unit (24) of the respective force-absorbing element (23) further comprises a spring (30) arranged in the respective cylinder (25).

9. Electrochemical device (10') according to one of claims 1 to 8, wherein a control unit (33) thereof automatically detects the operating state of the electrochemical device (10') depending on a measurement signal of at least one pressure sensor (32) and automatically controls the force application unit (13) depending thereon.

10. Electrochemical device (10') according to one of claims 1 to 9, wherein the same is designed as an electrolysis device (10') which, in an active operating state, produces hydrogen H2 and oxygen O2 from water H2O.

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